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Date: Thu, 25 Aug 2022 18:17:50 +0800
From: lizhe.67@...edance.com
To: vbabka@...e.cz
Cc: Jason@...c4.com, akpm@...ux-foundation.org, corbet@....net,
keescook@...omium.org, linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-mm@...ck.org,
lizefan.x@...edance.com, lizhe.67@...edance.com,
mark-pk.tsai@...iatek.com, mhiramat@...nel.org, mhocko@...e.com,
rostedt@...dmis.org, yuanzhu@...edance.com
Subject: Re: [PATCH v3] page_ext: introduce boot parameter 'early_page_ext'
On 25 Aug 2022 11:36:31 +0200, vbabka@...e.cz wrote:
>On 8/25/22 08:31, lizhe.67@...edance.com wrote:
>> From: Li Zhe <lizhe.67@...edance.com>
>>
>> In 'commit 2f1ee0913ce5 ("Revert "mm: use early_pfn_to_nid in page_ext_init"")',
>> we call page_ext_init() after page_alloc_init_late() to avoid some panic
>> problem. It seems that we cannot track early page allocations in current
>> kernel even if page structure has been initialized early.
>>
>> This patch introduce a new boot parameter 'early_page_ext' to resolve this
>> problem. If we pass it to kernel, function page_ext_init() will be moved
>> up and feature 'deferred initialization of struct pages' will be disabled.
>> It can help us to catch early page allocations. This is useful especially
>> when we find that the free memory value is not the same right after
>> different kernel booting.
>>
>> Changelogs:
>>
>> v1->v2:
>> - use a cmd line parameter to move up function page_ext_init() instead of
>> using CONFIG_DEFERRED_STRUCT_PAGE_INIT
>> - fix oom problem[1]
>>
>> v2->v3:
>> - make adjustments suggested by Michal Hocko
>>
>> v1 patch: https://lore.kernel.org/lkml/Yv3r6Y1vh+6AbY4+@dhcp22.suse.cz/T/
>
>IIRC v1 failed to boot in some automatic bot test. Will this not fail with
>the same config/hw combination when the parameter is passed?
There is no problem with or without the parameter now.
>
>> v2 patch: https://lore.kernel.org/lkml/20220824065058.81051-1-lizhe.67@bytedance.com/T/
>>
>> [1]: https://lore.kernel.org/linux-mm/YwHmXLu5txij+p35@xsang-OptiPlex-9020/
>>
>> Suggested-by: Michal Hocko <mhocko@...e.com>
>> Signed-off-by: Li Zhe <lizhe.67@...edance.com>
>> ---
>> Documentation/admin-guide/kernel-parameters.txt | 6 ++++++
>> include/linux/page_ext.h | 11 +++++++++++
>> init/main.c | 6 +++++-
>> mm/page_alloc.c | 2 ++
>> mm/page_ext.c | 12 ++++++++++++
>> 5 files changed, 36 insertions(+), 1 deletion(-)
>>
>> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
>> index d7f30902fda0..7b5726828ac0 100644
>> --- a/Documentation/admin-guide/kernel-parameters.txt
>> +++ b/Documentation/admin-guide/kernel-parameters.txt
>> @@ -1471,6 +1471,12 @@
>> Permit 'security.evm' to be updated regardless of
>> current integrity status.
>>
>> + early_page_ext [KNL] Boot-time early page_ext initializing option.
>> + This boot parameter disables the deferred initialization
>> + of struct page and move up function page_ext_init() in
>> + order to catch early page allocations. Available with
>> + CONFIG_PAGE_EXTENSION=y.
>> +
>> failslab=
>> fail_usercopy=
>> fail_page_alloc=
>> diff --git a/include/linux/page_ext.h b/include/linux/page_ext.h
>> index fabb2e1e087f..68d690649234 100644
>> --- a/include/linux/page_ext.h
>> +++ b/include/linux/page_ext.h
>> @@ -36,9 +36,15 @@ struct page_ext {
>> unsigned long flags;
>> };
>>
>> +extern bool early_page_ext;
>> extern unsigned long page_ext_size;
>> extern void pgdat_page_ext_init(struct pglist_data *pgdat);
>>
>> +static inline bool early_page_ext_enable(void)
>> +{
>> + return early_page_ext;
>> +}
>
>I think it should better be named early_page_ext_enabled() as it returns the
>status, not sets it to true?
Yes you are right. I will fix it in my v4 patch. Thanks!
>
>> +
>> #ifdef CONFIG_SPARSEMEM
>> static inline void page_ext_init_flatmem(void)
>> {
>> @@ -67,6 +73,11 @@ static inline struct page_ext *page_ext_next(struct page_ext *curr)
>> #else /* !CONFIG_PAGE_EXTENSION */
>> struct page_ext;
>>
>> +static inline bool early_page_ext_enable(void)
>> +{
>> + return false;
>> +}
>> +
>> static inline void pgdat_page_ext_init(struct pglist_data *pgdat)
>> {
>> }
>> diff --git a/init/main.c b/init/main.c
>> index 91642a4e69be..d95edb67a499 100644
>> --- a/init/main.c
>> +++ b/init/main.c
>> @@ -849,6 +849,9 @@ static void __init mm_init(void)
>> pgtable_init();
>> debug_objects_mem_init();
>> vmalloc_init();
>> + /* Should be run after vmap initialization */
>> + if (early_page_ext_enable())
>> + page_ext_init();
>> /* Should be run before the first non-init thread is created */
>> init_espfix_bsp();
>> /* Should be run after espfix64 is set up. */
>> @@ -1606,7 +1609,8 @@ static noinline void __init kernel_init_freeable(void)
>> padata_init();
>> page_alloc_init_late();
>> /* Initialize page ext after all struct pages are initialized. */
>> - page_ext_init();
>> + if (!early_page_ext_enable())
>> + page_ext_init();
>>
>> do_basic_setup();
>>
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index e5486d47406e..e580b197aa1e 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -482,6 +482,8 @@ defer_init(int nid, unsigned long pfn, unsigned long end_pfn)
>> {
>> static unsigned long prev_end_pfn, nr_initialised;
>>
>> + if (early_page_ext_enable())
>> + return false;
>> /*
>> * prev_end_pfn static that contains the end of previous zone
>> * No need to protect because called very early in boot before smp_init.
>> diff --git a/mm/page_ext.c b/mm/page_ext.c
>> index 3dc715d7ac29..bf4f2a12d7dc 100644
>> --- a/mm/page_ext.c
>> +++ b/mm/page_ext.c
>> @@ -85,6 +85,18 @@ unsigned long page_ext_size = sizeof(struct page_ext);
>>
>> static unsigned long total_usage;
>>
>> +#ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
>> +bool early_page_ext __meminitdata;
>> +#else
>> +bool early_page_ext __meminitdata = true;
>> +#endif
>> +static int __init setup_early_page_ext(char *str)
>> +{
>> + early_page_ext = true;
>> + return 0;
>> +}
>> +early_param("early_page_ext", setup_early_page_ext);
>> +
>> static bool __init invoke_need_callbacks(void)
>> {
>> int i;
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